Strap tensioning tool



March 5, 1963 A. J. KNOEBEL ETAL STRAP TENSIONING TOOL 3 Sheets-Sheet 1 Filed May 29, 1961 w #1 QR N mm QN March 5, 19 A. J. KNOEBEL ETAL STRAP TENSIONING TOOL Filed May 29; 1961 3 Sheets-Sheet 2 i!" ummy March 5, 1963 A. J. KNOEBEL ETAL 3,

STRAP TENSIONING TOOL Filed May 29, 1961 3 Sheets-Sheet 3 m\ g g R gmmzom lax z United States Patent 3,980,148. w 7 w STRAP TENSIONING TOOL A Alfred J. Knoebel, Worth, aild Marchand B. Hall, Olympia Fields, IiL, assignors to Acme Steel'Ctimpany,1Chi'- cago, Ill 3 corporationpf' Illinois Filed May 29, 1961, Ser. No; 113,228- 9 tllaims- (Gl. 254-51) This invention relates to the art of stretching or ten sioning' tools of a--typeused tostretchand tension a m'eta'l binder strap or bandencircled" inthefor-'r'n of a-loop around an object to be bound;

In the art of strap tensioning tools of the type mentioned, it is common to use a sharp toothed tensioning wheel or dog which is brought to bear against the strap and rotated to effect endwise movement of one end of the strap relative to its other end for the purpose of strap tensioning; The tensioning wheel is caused to rotate in different ways. Among them, rotation can be ca'usedb'y manually operated levers,,.air or hydraulic motors, or electric motors. Although electric motors have I been relatively widely used for strap tensioning in semi-automatic or automatic strapping machines, it is not as commom for hand tools because of the large size ofelectric motors ordinarily required. In disease of the strapping machines, the machine is largeand the electric motor is often used to perform several other functions in addition to strap tensioning. Therefore,- size is not too critical. In the case of a hand-tool, however, the smaller the-motor the'better in-order to minimize the weight of the tool and thereby minimize operator fatigue during use.

There has always been a strong desire'to-provide a'praca tical hand strap tensioning tool employing an electric motor because of the readily available sources of electricity. However, a major problem has been concerned with the inability to use other than-a relativelyheavy electric motor so that the entire weightof the tool is far greater than desired for a practical tool. There are electric motor driven strap tensioning hand tools available on the market, but they are all quite heavy and, so, the quantity in use is quite small compared to other types.-

It is the principal object of this invention to provide an improved hand strap tensioning tool employing. an electric motor for causing rotation of the tensioning wheel, which electric motor can be of small enough size to keep the weight of the motor and-tool down to a practical level.

On other tools embodying anelectric motor, the motor is necessarily large because it must-be capable of hen; dling full loads for prolonged time periods which requires that it be rated at highsustained current carrying capacity. The reason for this is that. the rinciple of operation involves continued rotation of the motor against aslipping clutch when'full tension on the strap isreached in order to maintain strap tensionuntil the strap is sealed and cut, after which the strap tension held by the tool can be relieved by shut-ting off the motor. It is another object of this invention to provide a check means for holding strap tension after it isreached so that'the electric motor can be shut off to relieve the load on it, thus reducing the time per cycle required for motor operation. This shorter operating time allows a motor with'a much smaller sustained current carrying capacityto be used and this considerably reduces the size-of the motor re quired to be used.

On other tools, the clutch used to connect the drive-of the motor to the tensioning wheel is. necessarily large" and heavy duty in order to withstand the constant force applied to'it when tension is reached asth'e tensioning wheel stops and the motor coritin'uesto operate in order to rnain tain' the straptension through the slipping clutch. It is an advantage of the check means for holding strap tenfsion of the tool of this invention that a-st'nalh size simple 3,080,148 Patented- Mar. 5; 1953 and light duty frictionclutch can be used-in order to further reduce the'weight of the tensioning tool.

Still another advantage of the reduced size of parts for the purpose of reducing weight is the over-all advantage of providing. a more economically manufactured tool which can be built and sold at lower cost.

Other objects and advantages of the invention should become apparent upon reference to the accompanying drawings, in which FIG. 1 shows a perspective view of a tensioning tool embodying principles of this invention as it appears in use when tensioning a strap around anobject;

FIG-2 shows-a topplan yiew partially cutaway and in partial section of atensioning tool like the one shown in FIG;

FIG. 3 shows a front end elevation of' the tool of G- 2;

BIG, 4" shows a sectional view along the line 44 of FIG. 2;

FIG. 5 isa sectional view along the line 5'-5of FIG. 2 and-shows the clutch mechanism which connects the motor drive to the tensioning wheel drive;

FIG; 6 shows a sectional view along the line 6-6 of G- 5;

FIG. 7 shows a view alongthe line FIG. 8 shows a sectional view along the line FIG. 5 7

FIG. 9 is a partial sectional view along the line 9-9 of FIG; 7; and

FIG. 1 0 is a view corresponding to theview'of FIG. 9 except that certain parts are shown in" different positions than in FIG. 9'. p

Asshown in FIG. 1, a terisio'nirig tool 1 embodying the principles" of this invention is" located in tensioning position on a packaged around which a loop'of metal strap 3 is encircled. The tool is positioned with strap 3 interposed between the strap seat 4 and the rotary tensi'oning wheel 5 of thetool 1'. T he't'ool is provided with an electric motor 6 which is caused to rotate'therotary tensioning'rwhe'el through an intermediate clutch and gear train as will hereinafter be described; As the rotary ten'sioning wheel 5 is' rotated, one end" of the strap 3 is moved relative to the other end in order to tighten the strap onto the package 2. After tensionin'g' iscompleted, the overlapping strap ends of the tensioned strap loop on the package are secured together by means" of a conventional sealing tool' which ordinarily deforms the strap ends into interlocking relationship with eachother, usually in combination with an in'terlocking tubular metal seal.

As shown in FIGS. 2", 3, 4 and 5, the motor 6 is connected' to a tubular housing 7 by means ofa threaded sleeve" 8. The shaft 9 of the motor 6' projects centrally intoxthis tubular housing 7 and its outer end- 9a is joinnaled in a bearing-10 mounted in a bore 11 of a clutch shaft 12. The outer end 9a which is journaled in the bearing 10' is circular in cross-section and reduc'edin diameter. However, the immediate portion 9b behind the end 9a is approximately rectangular incross-section. For convenience, it can=be manufactured'by providing two flat surfaces and 9d cut from a circular cross-section; Fitted'on-t'o this portion 9b are'three clutch driving discs 13, 1 s and 15 which have central openings through them corresponding to the modified rectangular shape of the portion 912" of the shaft; The corresponding modified rectangular shape of the shaft portion and the clutch driving discs maintains the discskeyed in a singular angular position on the shaft port-ion 9h. The disc 13' is prevented from sliding off of the end of the shaft by a retaining ring 16- mounted in a groove 17 of the shaft. Between the driving discs 1-3, 14- and 15 are mounted driven clutch discs 18 and 19. These disc's 18 and 19 are driven by' thefrict-ional force developedey pressing all of the discs toegther. The driven discs 18 and 19 have circular openings 18:: and 1% centrally where they fit over the shaft portion 1% so that they are free to rotate relative to the shaft 9.

The rear disc 15 is limited from reverse movement on the shaft by means of a drive pin 26 extending through the shaft 9. Forward movement of the discs for supplying squeezing pressure between the discs is urged by means of a compression spring 21 encircling the shaft 9 with its leading convolution 21a positioned on a shoulder 15a of the disc 15. The rear convolution 2115 of the spring 21 is positioned on a shoulder 22a of a collar 22 which is provided with a circular opening 23 which permits it to be fitted over the shaft 9. Behind the collar 22 is a gear 24 which has a central threaded bore 26a threada'oly engaging a threaded portion g) of the shaft 9. As the spring 21 urges the discs into contact with each other, it reacts against the collar 22 which in turn reacts against the gear 24. The gear 24 can be rotated relative to the shaft 9 which causes it to move one way or the other longitudinally of the shaft. By moving the gear 24 to the left, as viewed in FIG. 5, the spring 21 is compressed to cause tighter pressure between the clutch discs. If the gear as is moved to the right, the compression on the spring 21 is relieved and this reduces the pressure between the clutch discs.

As viewed in FIGS. 5 and 8, the surface of the gear 24 in contact with the collar 22 is provided with three spherical detents 24b which engage a ball 25 positioned in a spherical detent 26 in the collar 22. The purpose of this ball 25 is to maintain a fixed position of the gear 24 after it is rotated from one location to another along the length of the shaft 9. There are openings 27 and 28 provided in the housing 7 through which a screw driver or other device can be inserted to contact the teeth 24c of the gear 24 in order to rotate it on the shaft 9 and thereby adjust the compression of the spring 2 1 and, likewise, the pressure between the clutch discs 13, 14, 15, 18 and 19.

The driven clutch discs 13 and 19 are provided with radially projecting ends 18a and 19a which engage three slots 32a provided at the inner end of the clutch shaft in a flange portion 12b encircling the clutch discs. These projections 13a and 19a provide the actual driving connection between the clutch discs 18 and i9 and the clutch shaft i2.

The clutch shaft 12 is journaled in two ball bearings 28 and 29 mounted in a fixed position within sleeve 33 secured within the housing 7. The outer end 120 of the clutch shaft 12 is reduced in diameter and provided with an internally threaded bore 12d in which is threadably connected a coupling stud 31. This coupling stud is provided with an internal bore 31a and two slots 31b which engage a pin 32 (FIG. 2) for driving another coupling 33 keyed to the end of a shaft 37 leading to the gears which ultimately extend the drive of the electric motor to the strap tensioning wheel 5. A threaded tubular sleeve 34 on the outer end of the housing 7 is threadably engaged with the end 35 of the gear housing 36 to thereby connect the housing 7 to the gear housing as.

The shaft 37 is journaled in' two bearings 38 in the walls of the housing 36. This shaft 37 carries a pinion 39 keyed to it and the teeth of the pinion engage the teeth of a gear dtlto drive it. The gear it? is keyed to a shaft 41 which is journaled in bearing '42 in the housing 36 and the shaft 41 also carries a pinion $3. This pinion 43 engages and drives another gear 44 (FIG. 4) which is keyed to another shaft 45 which is journaled in bearings 46 in the gear housing. This shaft 45 also carries a pinion 47 which engages and drives another gear as keyed to a shaft 49 which is journaled in bearings 56 and 51 mounted in the housing 36. The outer end 52 of the shaft 49 protrudes beyond the gear housing 36 where it supports the strap tensioning wheel 5 above the strap seat 4. The strap tensioning wheel is secured onto the end 52 of the shaft 4? by means of a lock nut 53 which engages a threaded portion at the extreme shaft end. By this gear and pinion arrangement in the gear housing as, relatively high speed rotation of the shaft 9 driven by the motor 6 is reduced to a lower speed 0). the strap tensioning Wheel 5 with the advantage of high torque at the tensioning wheel 5 to provide the proper tensioning ability of the tool.

Pivoted on a pin 54 secured in the gear housing 36 is a lever 55. This lever can be pivoted in such a manner as to contact the lower surface 56 of a projection 57 on the upper portion of the strap rest plate *4. This stra rest plate 4 is pivoted on a shaft 58 so that this movement of the lever 55 causes pivotal movement of the strap rest plate 4 counterclockwise, as viewed in FIG. 3, to lower the actual strap engaging portion 5% of the strap rest plate 4 away from strap tensioning position closely adjacent to the periphery of the strap tensioning wheel 5. The clearance provided by this movement between the strap tensioning wheel 5 and the strap rest plate 4 allows for positioning of the strap ends between the two. When the lever 55 is released, a spring 66 secured around the shaft 5 reacts with the lever 55 to cause it to return to its initial position, and another compression spring 61 reacting between a portion or" the gear housing 36 and the upper portion of the strap rest plate 4 causes it to be returned in its clockwise position with its strap rest portion 59 closely adjacent to the periphery of the rotary tensioning wheel 5. With this positioning, the tool is ready to apply tension to the strap by causing the strap tensioning wheel 5 to be rotated.

As rotation of the straptensioning wheel 5 is effected by actuation of the motor 6, the clutch shaft 12 is rosated, as previously described. As viewed in FIGS. 5, 7, 9 and 10, the clutch shaft has a radially relieved cutout 62 in which is positioned a pawl 63. The pawl 63 is journaled on a shaft 64 which has its two ends 64a and 64b journaled in the side walls 65 of the recess 62. The pawl 63 has a corner 65 which is urged radially outwardly of the clutch shaft 12 as the pawl 63 is urged in a counterclockwise direction (FIG. 7) by force of a spring 67 reacting against a ball '68 in contact with the pawl 63. When the clutch shaft 12 is at rest, the corner 66 normally contacts one of three surfaces 69 which are side walls of three notches 76 provided along one edge of a ring 71. The ring 71 surrounds the clutch shaft 12 and is mounted for slight rotational movement against the inside circumferential wall 72 of the tubular housing 7.

At this time when the corner 66 of the pawl 63 engages one of the surfaces 69, the ring 71 is necessarily rotated to a position so that its three notches are in alignment with three notches 73 of the same width as that of the notches 70. These notches 73 are along an edge of the sleeve 39 facing the ring 71.

It is possible to disengage the corner 65 of the pawl 63 from its engaging surface 69 by causing the ring '71 to be shifted from its position as shown in FIG. 9 to its position as shown in FIG. 10 where the notches 70 of the ring 71 are brought out of alignment with the notches 73 of the sleeve 3%. The manner of causing shifting of the ring 71 is by means of movement of a lever 74 (FIGS. 1, 2 and 7) which is provided with two projecting teeth '75 and 76 which project into two small notches '77 and 73 of the ring 71. Upon downward movement of the lever 74, the projections 75 and 76 cause the ring 71 to be shifted from its position in FIG. 9 to that of FIG. 10. Upon reverse movement of the lever upward, the ring 71 is returned from its position shown in FIG. 10 to its position as shown in FIG. 9.

Ordinarily, as tensioning of the strap occurs, the motor causes the clutch shaft 12 to be rotated in the direction of the arrow '77 (FIG. 7). As this occurs, the ring 71 is held positioned with its notches 70 in alignment with the notches 73 of the sleeve 30, as viewed in FIG. 9. As the clutch shaft 22 increases its speed of rotation, the end 6321 of the'pawl 63 moves out radially by centrifugal force to remove the corner 66 from engagement with any of the surfaces 69. Without this movement, the'corner 66 would repeatedly {all into the notches 70 and 73 and provide a ratcheting noise as the pawl would be moved in and out. However, since the weight of the pawl end 63a removes this corner 66 from the vicinity of these notches, there is no ratcheting-effect which would create the undesirable ratcheting noise and wear on thecorner 66; As final tensioning of the strap is approached, the clutch parts tend to slip and the clutch shaft 12 slows down. As it slows down, the end 63a of the pawl moves radially inward and its corner 66 again moves radially outward-to begin a ratcheting in the notches 7d and 73; Assoon as tensioning-is reached,-the tensioning wheel stops and this indicates that the proper tension has been reached because of full slippage'of the clutchparts. At this time, the motor 6 is turned off to remove the driving power through the clutch to the clutch shaft 12. I'm riiediately the tension on the strap tends-to reverse rotation of the-clutch shaft, but the corner 66 of the pawl immediately'engagesthe next closest surface or one of the notches 7t) and also a forward surface 73a of a notch 73' in the sleeve 30. Thiskeepsthe clutch shaft from further reverse movement and maintains strap tension, even though the power is removed. The advantage of this is that the motor does not have-to be continued in operation and, so, its load rating can be reduced considerably and, therefore, the motor can be much smaller than usual.

After the tensioning is completed, the strap ends of the strap loop encircling whatever object is being strapped are joined together in a conventional manner by the use of a conventional joint forming tool. Thereafter, the lever '74 is depressed to rotate the ring 71 and disengage the corner 66' of the pawl from the surface 69 whichit engages. This allows the tension on the strap to :be relieved so that the tool can be removed from the object strapped in readiness for another strapping cycle.

Although only a single embodiment of the invention has been shown and described, it should be clearly understood that the invention can be made in many different ways without departing from the true scope of the invention as defined by the appended claims.

We claim:

1. In a strap stretching tool of a type having a tensioning wheel for engaging the strap and drawing it taut on an object comprising, a frame, a motor on the frame for powering the rotation of the tensioning wheel, a drive means interposed between the motor and the tensioning wheel for establishing a driving connection between the motor and the tensioning wheel, said drive means having a friction clutch consisting of circular driving discs frictionaily bearing against circular driven discs andnested therewith in a stack, said clutch having adjustable means for varying the maximum frictional force allowable between the driving and the driven discs before slippage between them occurs in order to control the maximum level of tension'developed in the strap being tensionedby rotation of the tensioning wheel, said adjustable means including acompression spring biased against the stack of nested driving and driven discs and provided with means for varying the compression of the compression spring against said stack, a pawl connected to said drive means and movable between a first position engaging a stop to prevent reverse rotation of the drive means and a second position clear of the stop to minimize wear of the pawl over the stop and to eliminate the noise of ratcheting of the pawl past the stop, the pawl being biased by a spring toward said first position and so weighted that it moves to its second position by centrifugal force developed upon rotation of the drive means when the motor rotates the tensioning wheel by means of the drive means, release means on said frame for causing the pawl to be disengaged from the stop when the drive means is stationary and there is no centrifugal force urging the pawl to its second position, said release means being in the form of a ring surrounding the drive means adjacent to an annular portion of the frame, said ring and annular portion having walls which together form said stop for the pawl when they are aligned witheach other, the angular relationship of the ring and annular portion being-changeable to misalign said walls and thereby prevent them fromacting as a stop for said pawl, I

2. In a strap tensioning tool as defined by claim 1 characterized by, saidmeans for varying the compression of said compression spring against said stack including a nut threaded onto a threaded drive shaft associated with the'drive means, said nut bearing against said compres sion spring and threadably movable along said drive shaft to adjust the compression of the compression spring.

3. In a strap tensioning tool as defined by claim 1 characterized by, said means for varying the compression of said compression spring against said stack including a nut threaded onto a threaded drive shaft associated with the drive means, said nut bearing against said compression spring and threadably movable along said drive shaft to adjust the compression of the compression spring, said nut being gear shaped with teeth at its periphery which can be contacted for manually adjusting. the nut on the drive shaft.

4. In a strap tensioning tool as defined by claim 1 characterized by, said means for varying the compression of said compression spring. against said stack including a nut threaded onto a threaded drive shaft associated with thedrive means, said not hearing against said compression spring and threadably movable along said drive shaft to adjust the'compression of the compression spring, said nut being provided with a spring detent for temporarily maintaining the nut in a fixed position along said drive'shaft.

5. In a strap tensioning tool as defined by claim 1 characterized by, said'means for varying the compression of said compression springagainst said stack including a nut threaded onto athreaded drive shaft associated with the drive means, said nut bearing against said compression spring and-threadably movable along said drive shaft to adjust the compression of the compression spring, said nut being gear shaped with teeth at its periphery which can be contacted for manually adjusting the nut on the drive shaft, said nutbeing provided with a releasable detent for temporarily maintaining the nut in a fixed position along said drive shaft.

6. In a-strap tensioning tool of a type having a tensioning wheel for engaging the strap and drawing it taut on an object comprising, a frame, power means on-the frame for causing rotation of the tensioning wheel, aclutch interposed between the power means and the tensioning wheelfor establishing a driving connection between the power means and the tensioning wheel,.said clutch'being of a type which slips when the resistance on the driven tensioning wheel due to the tension in the strapbein'g tensionedreaches a certain magnitude, said clutch having adjustable means for varying said certain magnitude re quired to cause clutch slippage, a pawl associated with said driving connection for the tensioning wheel which pawl ordinarily engages a stop to prevent reverse rotation of said tensioning wheel when the tensioning wheelis not rotating in its forward direction, said pawl being so weighted that it moves clear of said stop by reason of centrifugal force developed upon rotation of the driving connection during strap tensioning so that there is no noise of ratcheting of the pawl past the stop or wear of the pawl against the stop substantially during the strap tensioning period, release means on said frame for causing the pawl to become disengaged from the stop when the tensioning wheel is idle so that the ordinary gripof the tensioning wheel on the strap created when tensioning the strap can be relieved by allowing reverse rotation of the tensioning wheel, said release means being in the form of a ring surrounding the region of the pawl adjacent to sesame an annular portion of the frame also surrounding the region oi the pawl, said ring and annular portion having walls which together form said stop for the pawl when they are aligned with each other, the angular relationship of said ring and annular portion being changeable to misalign said walls and thereby prevent them from acting as a stop for said pawl.

7. In a strap tensioning tool of a type having a tensioning wheel for engaging the strap and drawing it taut on an object comprising, a frame, power means on the frame for causing rotation of the tensioning wheel, a clutch interposed between the power means and the tensioning wheel for establishing a driving connection between the power means and the tensioning wheel, said clutch being of a type which slips when the resistance on the driven tensioning wheel due to the tension in the strap being tensioned reaches a certain magnitude, said clutch having adjustable means for varying said certain magnitude required to cause clutch slippage, a pawl associated with said driving connection for the tensioning wheel which pawl ordinarily engages a stop to prevent reverse rotation of said tensioning wheel when the tensioning wheel is not rotating in its forward dir ction, said pawl being so weighted that it moves clear of said stop by reason of centrifugal force developed upon rotation of the driving connection during strap tensioning so that there is no noise of ratcheting of the pawl past the stop or wear of the pawl against the stop substantially during the strap tensioning period, release means on said frame for causing the pawl to become disengaged from the stop when the tensioning wheel is idle so that the ordinary grip of the tensioning wheel on the strao created when tensioning the strap can be relieved by allowing reverse rotation of the tensiouing wheel, said release means being in the form of a ring surrounding the region of the pawl adjacent to an annular portion of the frame also surrounding the region of the pawl, s id ring and annular portion having walls which together form said stop for the pawl when they are aligned with each other, said ring being angularly movable to shift its angular position relative to the annular region and cause said walls to become misaligned to thereby prevent them from acting as a stop for said pawl.

8. In a strap tensioning tool of a type having a tensioning wheel for en aging the strap and drawing it taut on an object comprising, a frame, power ieans on the frame for causing rotation of the tensioning wheel, a clutch interposed between the power means and the tensioning wheel for establishing a driving connection between the power means and the tensioning wheel, said clutch being of a type which slips when the resistance on the driven tensioning wheel due to the tension in the strap being tensioned reaches a certain magnitude, said clutch having adjustable means for varying said certain magnitude required to cause clutch slippage, a pawl associated with said driving connection for the tensioning wheel which pawl ordinarily engages a stop to prevent reverse rotation of said tensioning wheel when the tensioning wheel is not rotating in its forward direction, said pawl being so weighted that it moves clear of said stop by reason of centrifugal force developed upon rotation of the driving connection during strap tensioning so that there is no noise of ratcheting of the pawl past the stop or wear of the pawl against the stop substantially during the strap tensioning period, release means on said frame for causing the pawl to become disengaged from the stop when the tensioning wheel is idle so that the ordinary grip of the tensioning wheel on the strap created when tensioning the strap can be relieved by allowing reverse rotation of the tensioning wheel, said release means being in the form of a ring surrounding the region of the pawl adiacent to an annular portion of the frame also surrounding the region of the pawl, said ring and annular portion having walls which together form said stop for the pawl when they are aligned with each other, the an gular relationship of said ring and annular portion being changeable to misalign said walls and thereby prevent them from acting as a stop for said pawl, manually operated means on said frame for operating said release means by changing said angular relationship of the ring and the annular portion.

9. In a strap tensioning tool of a type having a tensioning wheel for engaging the strap and drawing it taut on an object comprising, a frame, power means on the frame for causing rotation of the tensioning wheel, a clutch interposed between the power means and the tensioning wheel for establishing a driving connection between the power means and the tensioning wheel, said clutch being of a type which slips when the resistance on the driven tensioning wheel due to the tension in the strap being tensioned reaches a certain magnitude, said clutch having adjustable means for varying said certain magnitude required to cause clutch slippage, a pawl associated with said driving connection for the tensioning wheel which pawl ordinarily engages a stop to prevent reverse rotation of said tensioning wheel when the tensioning wheel is not rotating in its forward direction, said pawl being so weighted that it moves clear of said stop by reason of centrifugal force developed upon rotation of the driving connection during strap tensioning so that there is no noise of ratcheting of the pawl past the stop or wear of the pawl against the stop substantially during the strap tensioning period, release means on said frame for causing the pawl to become disengaged from the stop when the tensioning wheel is idle so that the ordinary grip of the tensioning wheel on the strap created when tensioning the strap can be relieved by allowing reverse rotation of the tensioning wheel, said release means being in the form of a ring surrounding the region of the pawl adjacent to an annular portion of the frame also surround log the region of the pawl, said ring and annular portion having walls which together form said SLOP for the pawl when they are aligned with each other, said ring being angularly movable to shift its angular position relative to the annular region and cause said walls to become misaligned to thereby prevent them from acting as to stop for said pawl, manually operated means engaged with said release means to cause the angular movement of said ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,031 Brett Sept. 5, 1933 2,007,002 Porter July 2, 1935 2,685,350 Fall; Aug. 3, 1954 2,750,007 Turner et al June 12, 1956 

1. IN A STRAP STRETCHING TOOL OF A TYPE HAVING A TENSIONING WHEEL FOR ENGAGING THE STRAP AND DRAWING IT TAUT ON AN OBJECT COMPRISING, A FRAME, A MOTOR ON THE FRAME FOR POWERING THE ROTATION OF THE TENSIONING WHEEL, A DRIVE MEANS INTERPOSED BETWEEN THE MOTOR AND THE TENSIONING WHEEL FOR ESTABLISHING A DRIVING CONNECTION BETWEEN THE MOTOR AND THE TENSIONING WHEEL, SAID DRIVE MEANS HAVING A FRICTION CLUTCH CONSISTING OF CIRCULAR DRIVING DISC FRICTIONALLY BEARING AGAINST CIRCULAR DRIVEN DISCS AND NESTED THEREWITH IN A STACK, SAID CLUTCH HAVING ADJUSTABLE MEANS FOR VARYING THE MAXIMUM FRICTIONAL FORCE ALLOWABLE BETWEEN THE DRIVING AND THE DRIVEN DISC BEFORE SLIPPAGE BETWEEN THEM OCCURS IN ORDER TO CONTROL THE MAXIMUM LEVEL OF TENSION DEVELOPED IN THE STRAP BEING TENSIONED BY ROTATION OF THE TENSIONING WHEEL, SAID ADJUSTABLE MEANS INCLUDING A COMPRESSION SPRING BIASED AGAINST THE STACK OF NESTED DRIVING AND DRIVEN DISCS AND PROVIDED WITH MEANS FOR VARYING THE COMPRESSION OF THE COMPRESSION SPRING AGAINST SAID STACK, A PAWL CONNECTED TO SAID DRIVE MEANS AND MOVABLE BETWEEN A FIRST POSITION ENGAGING A STOP TO PREVENT REVERSE ROTATION OF THE DRIVE MEANS AND A SECOND POSITION CLEAR OF THE STOP TO MINIMIZE WEAR OF THE PAWL OVER THE STOP AND TO ELIMINATE THE NOISE OF RATCHETING OF THE PAWL PAST THE STOP, THE PAWL BEING BIASED BY A SPRING TOWARD SAID FIRST POSITION AND SO WEIGHTED THAT IT MOVES TO ITS SECOND POSITION BY CENTRIFUGAL FORCE DEVELOPED UPON ROTATION OF THE DRIVE MEANS WHEN THE MOTOR ROTATES THE TENSIONING WHEEL BY MEANS OF THE DRIVE MEANS, RELEASE MEANS ON SAID FRAME FOR CAUSING THE PAWL TO BE DISENGAGED FROM THE STOP WHEN THE DRIVE MEANS IS STATIONARY AND THERE IS NO CENTRIFUGAL FORCE URGING THE PAWL TO ITS SECOND POSITION, SAID RELEASE MEANS BEING IN THE FORM OF A RING SURROUNDING THE DRIVE MEANS ADJACENT TO ANNULAR PORTION OF THE FRAME, SAID RING AND ANNULAR PORTION HAVING WALLS WHICH TOGETHER FORM SAID STOP FOR THE PAWL WHEN THEY ARE ALIGNED WITH EACH OTHER, THE ANGULAR RELATIONSHIP OF THE RING AND ANNULAR PORTION BEING CHANGEABLE TO MISALIGN SAID WALLS AND THEREBY PREVENT THEM FROM ACTING AS A STOP FOR SAID PAWL. 